apache/druid · error · java.lang.UnsupportedOperationException

StringFirstAggregator does not support getLong()

Error message

StringFirstAggregator does not support getLong()

What it means

StringLastBufferAggregator cannot produce a long from its stored timestamp/string pair, so getLong(ByteBuffer,int) throws UnsupportedOperationException. This enforces that string aggregators are consumed through their string result path.

Solutions

Extract the value via get(ByteBuffer,int) (the string pair) instead of getLong
Choose a numeric aggregator (longFirst/longLast) when a long is needed
Check AggregatorFactory.getTypeName() and only call the matching typed accessor
Apply SQL CAST(... AS BIGINT) if the string should be interpreted as a long

Example fix

// before
long l = bufAgg.getLong(buf, position); // throws
// after
Object val = bufAgg.get(buf, position); // string result
long l2 = Long.parseLong((String) val); // only if conversion intended

Defensive patterns

Strategy: type-guard

Validate before calling

if ("long".equals(factory.getTypeName())) { l = bufAgg.getLong(buf, pos); } else { /* string path */ }

Type guard

static boolean hasLongAccessor(AggregatorFactory f) { return f.getTypeName().equals("long"); }

Try / catch

try { l = bufAgg.getLong(buf, pos); } catch (UnsupportedOperationException e) { l = 0L; }

Prevention

Check the metric type before integer result extraction
Use longFirst/longLast for integer aggregations
Convert string results explicitly (parseLong) when numeric output is intended

When it happens

Trigger: Calling getLong(buf, position) on a StringLastBufferAggregator instance during result collection when the metric is assumed numeric.

Common situations: Generic result merge/extraction code in custom extensions; tests that call all three numeric accessors on every buffer aggregator; SQL plans that expect a numeric type but were given stringFirst/stringLast.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/336143f56240be4d. Report an issue: GitHub.

Appendix: source

Thrown at processing/src/main/java/org/apache/druid/query/aggregation/firstlast/last/StringLastBufferAggregator.java:121

    }
  }

  @Override
  public Object get(ByteBuffer buf, int position)
  {
    return StringFirstLastUtils.readPair(buf, position);
  }

  @Override
  public float getFloat(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("StringFirstAggregator does not support getFloat()");
  }

  @Override
  public long getLong(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("StringFirstAggregator does not support getLong()");
  }

  @Override
  public double getDouble(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("StringFirstAggregator does not support getDouble()");
  }

  @Override
  public void close()
  {
    // no resources to cleanup
  }

  @Override
  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
  {
    inspector.visit("timeSelector", timeSelector);

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